This invention relates to a method and apparatus for collecting weighed articles discharged from a combinatorial weighing system.
A combinatorial weighing system generally has a plurality of weighing machines and operates by computing combinations based on weight values obtained from the weighing machines, selecting a combination of weights which, when summed, gives a total value equal to a set weight or set number, or closest to the set weight or set number within preset allowable limits, and discharging weighed articles from the weighing machines belonging to the selected combination. In the prior art, the discharged articles are collected in a manner which will now be described.
As shown in FIG. 1, each of the weighing machines in the combinatorial weighing system is composed of a weighing hopper and a weight sensor associated therewith. The weights of articles supplied into these weighing hoppers A.sub.1, A.sub.2,... A.sub.n are measured by the associated weight sensors B.sub.1, B.sub.2,... B.sub.n, the total weights of all possible combinations of the weighed articles are computed, with the number of weight values in each combination being arbitrary or predetermined, the total weight values are compared with a set weight serving as a target, a combination is selected giving a total combined weight equal to the set weight or closest to the set weight within preset allowable limits, the articles in the weighing hoppers associated with the selected weighing machines are discharged into a collecting chute C, and the discharged articles are collected at the bottom of the chute centrally thereof and then introduced into a timing hopper D where the articles are recovered.
Alternatively, the weight values found by the weight sensors B.sub.1, B.sub.2,... B.sub.n are divided by the unit weight of the articles to give the number of articles in each weighing hopper, different combinations of article numbers are added to obtain a number of the articles equal or closest to a set number, and these articles are discharged from their weighing hoppers and recovered.
Although high accuracy can be realized in either case, there is increasing demand for a combinatorial weighing system with a higher weighing capacity. To improve weighing capacity, it is necessary to elevate the rate of supply and the measuring speed. In addition, it is of utmost importance that the weighed articles, which are discharged at the end of each weighing operation and then slide along the chute C under their own weight, be collected and discharged from the system efficiently.
To this end, various collecting chute configurations have been devised, as shown by way of example in FIGS. 2 through 4. The chute shown in FIG. 2 comprises a collecting chute 3 having an inlet opening 1 and a discharge opening 2, an an intermediate shutter 4 suspended above the discharge opening 2. A predetermined number of weighing hoppers A are arranged circumferentially above the inlet opening 1 of the collecting chute 3. Articles are discharged from the weighing hoppers A on opening the hoppers and are collected by the collecting chute 3 and supplied to a timing hopper D disposed below the collecting chute 3. The intermediate shutter 4 is raised and lowered depending upon the rate at which the articles slide downwardly along the chute 3. Thus, the shutter 4 separates the articles currently discharged from the weighing hoppers A from the articles discharged at the end of the previous weighing cycle, the separation taking place at the mid-portion of the collecting chute 3. Articles which the shutter 4 has allowed to pass are recovered in the timing hopper D.
It should be noted that there are situations where the timing hopper D is not provided because of a connection between the combinatorial weighing system and a packaging machine associated therewith. In such case the articles are introduced into the packaging machine directly from the chute, or a distributing device is provided for operatively linking the single combinatorial weighing system with two packaging machines.
In the arrangement provided with the shutter 4, combinatorial weighing can take place at a rate higher than that ordinarily obtained. By virtue of the intermediate shutter 4 provided at the mid-portion of the collecting chute 3, articles previously discharged are not permitted to mix with articles currently discharged, so that articles released by the weighing hoppers A at the end of each weighing cycle can be recovered in the timing hopper D in good order regardless of the higher rate of the combinatorial weighing operation.
However, when the collecting chute 3 is constructed in the above-described manner, it is necessary to provide a mechanism for vertically displacing the intermediate shutter 4 in synchronism with the opening and closing of the weighing hoppers A, thus complicating the construction of the apparatus. Moreover, the article discharge capacity cannot be increased beyond a certain limit because the collecting chute 3 is provided with movable portions.
In addition, since the collecting chute 3 has only one discharge opening 2, it is necessary to provide a distributing device when the combinatorial weighing system is operatively linked with a twin-tube packaging device. In such case, the distributing capacity of this device poses a major problem.
FIGS. 3 and 4 show an example of the conventional separate-type collecting chute having a discharge passage separated or divided into two routes. An inner chute section 5 and an outer chute section 6 of inverted frusto-conical shape are arranged to intersect each other so that respective upper supply openings 7, 8 thereof are arranged concentrically and respective lower discharge openings 9 and 10 are arranged in side-by-side relation. The narrow discharge passage defined between the outer chute 6 and inner chute 5 is partially cut out. Thus, the collecting chute has two independent discharge passages.
The operation of the arrangement shown in FIGS. 3 and 4 will now be described. The combinatorial weighing system includes a predetermined number of weighing hoppers B having a double-door construction and dual discharge openings arranged along the upper rim of the supply openings 7 and 8 of the inner and outer chutes 5 and 6. The weighing hoppers B of the double-door construction release their articles into whichever of the inner and outer chutes 5 or 6 is designated. The weighed articles are collected separately by these chutes which in turn discharge the articles separately.
With this arrangement, the configuration of the inner and outer chutes 5 and 6 is complicated. Moreover, as illustrated in the drawings, all of the weighing hoppers cannot release their articles exclusively into the inner chute 5 or outer chute 6 by the opening of double doors. Those weighing hoppers B' arranged above the inner chute 5 where the outer chute 6 has been cut out must necessarily be of single door type, and the discharge route for these weighing hoppers is limited to the inner chute 5. This places a limitation upon the combinatorial computations, and great difficulty may be experienced in terms of accuracy and function when the combinatorial weighing system is to be operatively linked with a pair of simultaneously operating packaging machines and a pair of alternating or independently operating packaging machines.
As shown in FIG. 5, it may be contemplated to have the entire circumference of the inner chute 5 surrounded by the outer chute 6 so that the weighed articles may be discharged from any of the weighing hoppers B into either of the chutes 5 and 6. With this arrangement, however, the inner and outer chutes 5 and 6 have different discharge capacities owing to a difference in the rate at which weighed articles slide downwardly therealong. This is because the sloping surfaces of the inner and outer chutes 5 and 6 have widely different angles of inclination. Indeed, the angle of inclination of the sloping surface differs for different portions of the same chute. In addition, a narrow discharge passage is formed at the intersection of the outer chute 6 and inner chute 5, thereby hampering the discharge of articles from the outer chute 6.